The present invention relates generally to the utilization of ultrasonic sound waves and a light curtain in combination to take dimensional measurements of objects and, more specifically, to a method and apparatus for ascertaining three-dimensional measurements and/or volume of objects.
Millions of packages per year are handled and shipped by United Parcel Service, Federal Express, and many other smaller courier and delivery services. These packages originate with federal, state, and local governments as well as private businesses of all sizes. In many instances, the charges by the carriers to their customers are based on the so-called "dim-weight factor" or "dimensional weight factor" (DWF) of the article being shipped, a fictitious dimension based on length times width times height in inches divided by a standard agency or association-recognized divisor or conversion factor, commonly 166 (L.times.W.times.H.div.166). The "166" divisor or conversion factor has been recognized and adopted by the International Air Transport Association (I.A.T.A). Even if an object or package is of irregular configuration, the dim weight, using the longest measurement each of length, width, and height, is still utilized for billing purposes. The volume computed by multiplication of object length times width times height may hereinafter be termed the "cubic volume," "spatial volume," or simply the "cube" of the object.
The measurements of the articles shipped is also critical so that the carrier can accurately determine the number of trucks, trailers, or other vehicles which will be required to transport goods to their destinations and so both customers and carriers can accurately estimate their warehousing and other storage needs.
In addition, article weight and measurements are also used to determine and predict weight and balance for transport vehicles and aircraft and to dictate the loading sequence for objects by weight and dimensions for maximum safety and efficiency.
Further, if orders of any items are to be packed into boxes, knowledge of object weight and dimensions would be useful for selecting box size and durability.
To date, it has been a common practice for the customer to manually "cube" or measure boxes or other articles with a ruler, yardstick, or other straightedge marked with units of length, generally inches, perform a calculation for "dim weight," and provide same to the carrier with the package. If the customer does not "cube" the articles, then the carrier performs the operation. Since these measurements and calculations are generally done hurriedly, there is an equal chance that the customer will be under or over charged. To add to the problem, there are many packages and other objects not susceptible to even a grossly accurate manual measurement of dim weight, for example and not by way of limitation, loaded pallets, tubes, drums, reels of hose, cable or wire, etc. Many machine and automotive parts are shipped "naked" with tags attached or, at most, bagged or shrink wrapped. It is obvious to one skilled in the art that a straightedge measurement to ascertain the greatest extent of each dimension will not be accurate in any of these instances to any degree whatsoever.
It is known to the inventor that a "jig"-type measuring system for packages has been used, with a base and two sides joining in a corner at 90.degree. angles, each marked with gross dimensional units (to the nearest one inch) so that a cubic package can be placed on the base at the corner and measurements taken manually by looking at the markings and recording same, but again, the accuracy is limited by the care and eyesight of the measurer, and the time utilized is unreasonably long when thousands of packages are being shipped, as with Sears, K-Mart, or other large retailers.
In short, a quick, accurate means and method for determining the dimensions and the cubic volume or spatial volume of packages and other objects in a commercial or industrial setting has been lacking for many situations.
U.S. Pat. No. 5,042,015, assigned to the assignee of the present application, discloses a practical and commercially successful means and method for object measuring. However, the patented method and apparatus requires, for measurement of moving objects, that the objects be aligned with respect to the path of movement. Thus, there existed a need for a system for measurement of skewed objects. To the best of the inventors' knowledge, only one such commercially offered system exists, and is described in U.S. Pat. No. 4,773,029. The system of the '029 patent, however, senses the apparent dimension of the moving object solely through the use of infrared emitter-receiver arrays, and establishes the true length and width of an object by periodic measurements which provide "slices" of the object, the slices then being summed to provide a horizontally planar footprint of the object from which the true length and width are measured. The inventors have no knowledge as to whether the system in fact works as described in the patent, but its advertised cost makes it prohibitively expensive, beyond the capabilities of many businesses, and a financial burden on those companies able to afford it.
U.S. patent application Ser. No. 07/671,256, filed on Mar. 18, 1991 and assigned to the assignee of the present invention, provides an alternative to the system of the '029 patent. The application discloses and claims a method and apparatus for determining the actual length and width dimensions of a linearly moving rectangular object by determining apparent length, apparent width, and the distance between an object corner facing to the side of the travel direction and the trailing edge of the object. These measurements were then employed to determine the actual object length and width via trigonometrically-based mathematical equations. The methodology as described in the '256 application has been proven to be sound, as have the mathematical relationships, but the apparatus described in the application employed to obtain the dimensions has been found lacking as to the accuracy desired by the inventors.